Ground-state structures, vibrational frequencies, HOMO-LUMO energy gap, electron affinities, and cluster mixing energy of binary semiconductor clusters SimGen in the range s = m + n <= 7 have been investigated using the B3LYP-DFT and CCSD(T) methods with the basis of 6-311+G(d). SimGen clusters are found to have similar structural patterns and the same spin multiplicities as those of corresponding elemental clusters of Si-s and Ge-s but with more isomeric structures and lower symmetries. Notable structural changes induced by the additional electron were observed, except for s = 4. The mixing energies of binary clusters are negative, which suggests that the mixed clusters are more stable than pure Si and Ge clusters. Both the HOMO-LUMO gaps and the calculated mixing energy show that binary clusters SiGe2, Si2Ge2, Si2Ge3, Si2Ge4, and Si2Ge5 are species with high stability and more likely to be produced experimentally.